Zolpidem (Ambien ) is a commonly prescribed sleep-aid that exhibits selectivity for benzodiazepine (BZ)/GABAA receptors containing the alpha-1 subunit Previous studies have suggested that zolpidem has a characteristic profile of subjective effects that differ from those of conventional BZ agonists The present study assessed the ability of BZs and barbiturates, which typically share interoceptive effects with BZs, to reproduce the effects of zolpidem in squirrel monkeys trained to discriminate zolpidem from vehicle The effects of zolpidem also were assessed in squirrel monkeys trained to discriminate another sleep-aid, triazolam (Halcion ) Under test conditions, zolpidem engendered a dose-dependent increase in zolpidem-lever responding, reaching an average maximum of r80% Triazolam and diazepam also engendered r80% zolpidem-lever responding However, other BZ agonists including chlordiazepoxide and lorazepam, as well as the barbiturates pentobarbital, bar bital, and methohexital, engendered maximums of only 20-70% zolpidem-lever responding up to doses that markedly reduced response rate In contrast, zolpidem, chlordiazepoxide and lorazepam substituted fully in monkeys trained to discriminate triazolam using a similar procedure These results suggest that zolpidem's selectivity for the alpha-1 subunit of the BZ/GABAA receptor complex confers a profile of interoceptive effects that is unique compared to typical BZ agonists